Elastic fluid turbine



Patented June 21, 1938 ELASTIC FLUID TURBINE Glenn B. Warren, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application January 17, 1936, Serial No. 59,579

2 Claims.

The present invention relates to elastic fluid turbines, more specifically to turbine arrangements from which elastic fluid is tapped or extracted from the last stages of the turbine, that is, ahead of the last bucket wheel as regards the direction of flow through the turbine. Aside from arrangements where the extracting is carried out primarily to use the extracted steam for indus trial purposes, such extracting may have a twofold purpose. First, to dewater the elastic fluid flowing through the last stages, that is, reduce its moisture content, and second, to enable the turbine to handle the large amount of elastic fluid flowing through the last stages at high load condition.

The object of my invention is to provide an improved construction and arangement of the type of turbines above specified, whereby fluid flowing through the last stage or stages of the turbine is effectively dewatered or freed from its moisture content and a part of the elastic fluid bypassed with regard to the last stage or stages, to prevent damage to the bucket blades of the last wheel or wheels.

For a consideration of what I believe to be novel and my invention, attention is directed to the following description and the claims appended thereto in connection with the accompanying drawing.

The single figure of the drawing represents a sectional view of an elastic fluid turbine in accordance with my invention.

The arrangement comprises a turbine rotor having a shaft 1 ii and a plurality of bucket wheels secured thereto. In the present instance I have indicated a higher or preceding stage bucket wheel H and a lower or last stage bucket wheel l2. Each bucket wheel has a row of buckets l3 secured at their inner ends to disk members and 40 held together at their outer ends by a ring or shroud band I4 or the like. Elastic fluid flowing through the turbine is directed to the bucket wheel I l by a diaphragm l5 having a plurality of nozzle-defining partitions l6, and elastic fluid discharged from the bucket wheel H is directed to the bucket wheel l3 by a nozzle diaphragm I! having nozzle-defining partitions H8. The nozzle diaphragms I5 and H form a part of the stator and are secured to and held in position by an outer casing IS. The exhaust end of the casing has a flange 20 secured to a flanged exhaust hood 2| for conducting the exhaust fluid to a condenser or the like. For our present purposes the exhaust hood 2| may be considered a part of the condenser. As the elastic fluid flows through the turbine its pressure decreases and its volume consequently increases. Likewise the moisture content of the elastic fluid is increased. In order to prevent injurious effect of the moisture content and to enable the turbine to handle the large amounts of elastic fluid flowing through the lower stages at high load, means are provided to bypass, bleed, or extract a part of the elastic fluid from the lower stages. These means include channels or chambers 22 and 23 for receiving a part of the stream of elastic fluid before being passed into the last stages. Elastic fluid is conducted to the channels 22 and 23 from the outer region of the stream of fluid, whereby the fluid having the greater moisture content is separated from the main stream of fluid. The fluid is conducted into the channels 22 and 23 through throttling passages 24 and 25. respectively. The passages 24, 25 and the channels or chambers 22, 23 in accordance with my invention are formed by adjacent surfaces of the casing I 9 and the nozzle diaphragms i5, I1. The chambers 22, 23 may discharge in known manner to the condenser or other suitable point, not shown.

Another important feature of my invention is the provision of the last stage bucket wheel l2 which has an outer diameter smaller than the outlet diameter of the nozzle diaphragm l 1. From another viewpoint, the nozzles of the diaphragm IT project radially beyond the bucket wheel l2. A passage 26 is thus defined between the outer surface of the shroud band I l and the inner surface of the casing IQ for receiving fluid from the outer region of the stream flowing through the nozzles of the diaphragm I1. This fluid is bypassed with regard to the bucket wheel [3.

In order to reduce leakage losses around the tip formed by the shroud band M of the bucket wheel [2, I may provide a partition 21 having a ring portion surrounding the shroud band I4 and closely spaced therewith and another portion disposed within the nozles defined by the partitions E8 of the diaphragm H. The partition 21 may be secured to the nozzle partitions or blades I8 of the nozzle diaphragm H by means of welds 28 on the outer surface of the partition 21.

Having described the method of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A multi-stage axial flow elastic fluid turbine including the combination of a casing, a rotor having a last stage bucket wheel with a plurality of buckets, a last stage nozzle diaphragm supported on the casing and having a plurality of nozzles for directing elastic fluid to the buckets, and a channel and throttling means defined by adjacent surfaces of the last stage nozzle diaphragm and the casing to receive a part of the elastic fluid flowing through the turbine before it enters the nozzles of the last stage diaphragm, the outlet diameter of the nozzles of the last stage nozzle diaphragm being greater than the outer diameter of the buckets of the last stage bucket wheel to bypass a part of the fluid flowing through the diaphragm with regard to the last stage bucket Wheel.

2. A multi-stage axial flow elastic fluid turbine including the combination of a rotor having a last stage bucket wheel with a plurality of buckets, a casing, a last stage diaphragm adjacent the bucket wheel being held on the casing and having a plurality of nozzles for directing elastic fluid to the last stage wheel, the nozzles of the last stage diaphragm projecting radially beyond the buckets of the last stage bucket wheel to cause part of the fluid flowing through the nozzles to bypass the bucket wheel, and a partition having a portion closely spaced with and surrounding the last stage bucket wheel and another portion disposed within the nozzles of the last stage diaphragm and secured to the diaphragm to reduce leakage losses around the tip of the bucket wheel.

GLENN B. WARREN 

